: No real difference from in a wood floor other than you're going to have to break concrete. Basically, the toilet rough in is 12" from the back wall to the center of the flange. The flange connects to a closet bend and then to pipe to the sewer line. If you have more than 6 feet between the toilet and the sewer, you will have to add a vent which will likely mean more concrete breaking. The drain must slope 1/4" per foot to the sewer and if you have to make a direction change, make it as gradual as possible. The water supply comes in 8" from center and 8" above the floor, although you can vary this if necessary. When you get the pipe in the proper position, leave a few inches of pipe out of the floor. Replace the concrete and level it, but leave a space around the pipe where the flange is to go. The flange sets on the finished floor (if there is to be one) That's about it.